Eight of the best brainteasing maths puzzles we could find

In the past month, the world has been gripped by a series of maths and logic puzzles that were originally set for children.

First came the parked car puzzle which was set as a test for primary school children in Hong Kong but many adults still found tricky to solve.

Then came Cheryl's birthday, set for 15 to 16-year-olds in Singapore but seemingly impossible for anyone to solve. And finally this week came the rod and string conundrum which stumped 96 per cent of top maths students in the US when it first appeared back in the 1990s.

Because all have proved so popular, and many of you seem to have already solved the original three, we've pored through the records to find eight more puzzles to leave you chewing your pencil and pulling out your hair.

On the first day of term the headteacher asks the first student to go along and open every single locker, he asks the second to go to every second locker and close it, the third to go to every third locker and close it if it is open or open it if it is closed, the fourth to go to the fourth locker and so on.

The process is completed with the thousandth student. How many lockers are open at the end?